Changing Plan Owner

Hello all,

I'm trying to change the owner of a plan, specifically to migrate it from a corporate executive to the company itself. I found this thread and tried to do a simple update to T_Plans (in TEST) in SSMS with the following code:

update dbo.T_PLAN
set customer_no=165111
where plan_no=1765

but it returned the following error message:

Msg 2601, Level 14, State 1, Line 1
Cannot insert duplicate key row in object 'dbo.T_PLAN' with unique index 'UQ_T_PLAN_campaign_fund_designation_customer'. The duplicate key value is (703, 239, -1, 165111).
The statement has been terminated.

I'm wondering if there has been a change in how the table is keyed that would prevent this update from being possible, and if anyone has any other ideas on how to accomplish this change.

Thanks,

Megan